1. Field of the Invention
The present invention relates to an engine equipped with an adjustable valve timing mechanism preferably used in an automobile.
2. Description of the Related Art
There has been conventionally known a reciprocating engine (hereinafter simply called engine) which is used in an automobile and which is equipped with a mechanism to vary dynamic characteristics (valve lifting characteristics) of inlet valves and exhaust valves such as opening/closing timings, opening terms and lifting amounts.
This mechanism is called an adjustable valve timing mechanism, an example of which is disclosed in Patent Reference 1 below.
Patent Reference 1 discloses a technique to vary the valve lifting characteristic of the inlet valves and the exhaust valves according to the load and the speed of the engine with the intention of improvement in the fuel efficiency and the engine power.
[Patent Reference 1] Japanese Patent No. 3094762.
However, recent growth of interest in environmental protection demands further improvement in fuel efficiency, which the technique in Patent Reference 1 cannot satisfactorily provide. Further, even if the fuel efficiency is improved, decline in the engine output is unfavorable because the original convenience of automobiles would be impaired.